RE: Passing lisp vector to foreign code

Thanks. Here's how I got it working:

Outbound:

(let ((buf (output-buffer self))
      (bufsiz (buffer-size self)))
  (fli:with-dynamic-foreign-objects ()
    (let ((vector (fli:allocate-dynamic-foreign-object :type `(:c-array
(:unsigned :char) ,bufsiz))))
      (dotimes (i bufsiz)
        (setf (fli:foreign-aref vector i) (aref buf i)))
      (put-bytes db vector bufsiz)

Inbound:

with-slots ((buf buffer)
             (len bufsiz)) self
  (multiple-value-bind (bytes nbytes)
      (get-bytes db)
    (let ((contents (loop for i from 0 below nbytes collect (fli:dereference
bytes :index i))))
      (setf buf (make-array nbytes :initial-contents contents))
      (setf len (length buf)))))

Look reasonable?

dey

-----Original Message-----
From: Martin Simmons [mailto:martin@lispworks.com]
Sent: Thursday, July 28, 2005 1:10 PM
To: deyoung@bloodhoundinc.com
Cc: lisp-hug@lispworks.com
Subject: Re: Passing lisp vector to foreign code


>>>>> On Wed, 27 Jul 2005 11:26:44 -0400, "Young, David"
<deyoung@bloodhoundinc.com> said:

  dey> So, I have a binary stream class that collects bytes into a buffer
  dey> represented by a vector with a fill pointer. I want to take this
buffer and
  dey> send it to a C function, which stores it in a "database". Later, I
want to
  dey> retrieve this data via another binary stream class (we're
experimenting with
  dey> CL-STORE). Using the lw ffi, how do I set this up? It seems from the
docs
  dey> that I need to make a copy of the buffer in static space prior to
sending it
  dey> to C; is that correct? What should the ffi function declarations look
like?
  dey> Currently, I have:

  dey> (fli:define-foreign-function
  dey>     (put-bytes "put_bytes" :source)
  dey>     ((bytes (:c-array (:unsigned :char)))
  dey>      (len :int))
  dey>   :result-type :void
  dey>   :calling-convention :cdecl)

  dey> (fli:define-foreign-function
  dey>     (get-bytes "get_bytes" :source)
  dey>     ((nbytes (:pointer (:int))))
  dey>   :result-type (:c-array (:unsigned :char))
  dey>   :calling-convention :cdecl)

  dey> But, passing a Lisp vector to PUT-BYTES yields a type error:

  dey>   Expecting type (:foreign-array (:UNSIGNED :CHAR) (0)) (got #(76
....))

  dey> so clearly I'm doing something wrong. Thanks for the help.

There are two kinds of static array: Lisp and foreign.  The :C-ARRAY foreign
type needs a foreign array object (e.g. created with
FLI:ALLOCATE-FOREIGN-OBJECT).  See also the :LISP-ARRAY foreign type if you
want to pass a static Lisp array pointer directly to C.

-- 
Martin Simmons                              Email: martin@lispworks.com
LispWorks Ltd, St John's Innovation Centre    TEL:   +44 1223 421860
Cowley Road, Cambridge CB4 0WS, England.      FAX:   +44 870 2206189

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